Thanks for your decent reply. I've been in the trade for 34 years ( yes, old boy 62), I call the exterior back wall to the bedroom a window wall.
Gypsum have over the years produced there crap and I've called, written or emailed to say what the f@#k is this s**t. I have done so on this occasion of this ridiculous speed of the plaster.
I single Handley could do a 16ft x12ft ceiling no problem with the other plaster, but this new fast stuff, you'd require two plasters and a labourer.
Madness. They can't stop messing, Gypsum. Never know when they got a quality product. Lol.